SANFORD - Neighborhood Watch volunteer George Zimmerman spotted an innocent teenager and assumed he was about to commit a crime so he followed him, murdered him then made up a series of lies hoping to avoid arrest, a prosecutor told jurors Thursday.

"He brought a gun to a struggle that he had started," Assistant State Attorney Bernie de la Rionda told jurors during closing argument, "and now he wants you to let him off because he killed the only eye-witness."

Jurors are expected to begin deliberations Friday afternoon in the most-watched trial in the country. There could be a verdict by nightfall Friday.

The panel of six women — five of them white — must decide whether Zimmerman committed second-degree murder, manslaughter or acted in self-defense when he killed 17-year-old Trayvon Martin in Sanford on Feb. 26, 2012.

When court resumes at 8:30 a.m., defense attorney Mark O'Mara is expected to give a three-hour closing argument, his last chance to save Zimmerman from a long prison term.

If convicted of second-degree murder Zimmerman faces up to life in prison. If found guilty of manslaughter he could be sentenced to up to 30 years.

In recent weeks O'Mara has predicted an acquittal.

The jury has listened to three weeks of testimony from nearly 60 witnesses and watched as attorneys presented 250 evidence exhibits. They have lived together in a hotel, sequestered from their families, friends, jobs and media reports since testimony began June 24.

De la Rionda gave an unconventional closing argument. He did not tell jurors what happened in the seconds just before the shooting. He conceded he did not know.

Instead he offered possibilities: that Zimmerman had his 9mm handgun in his hand as he walked through the neighborhood, trying to find Trayvon or that the defendant had pulled Trayvon toward him by the drawstring of the teen's hoodie just before shooting him.

De la Rionda accused Zimmerman of profiling Trayvon but said almost nothing about race, the issue that sent protesters into the streets last year and brought the Revs. Al Sharpton and Jesse Jackson to Sanford for marches and rallies.

Zimmerman "profiled him as a criminal. He assumed certain things, that Trayvon Martin was up to no good, and that is what led up to his death," de la Rionda said.

The prosecutor did, however, make a reference to the Rev. Martin Luther King Jr., when he projected a PowerPoint slide onto the wall as he defended the testimony of the state's most important witness — Rachel Jeantel, who was on the phone with Trayvon seconds before the shooting.

Jeantel created a sensation when she testified, not because of her account but because she used slang, was defiant at times and spoke so softly and fast she was difficult to understand.

A witness should be judged, said de la Rionda's slide, "not on the color of her personality but on the content of her testimony."

On Thursday morning, Circuit Judge Debra S. Nelson ruled that jurors would be able to consider manslaughter as a possible verdict.

But moments later defense attorney Don West went ballistic after the state asked the judge to allow another possibility: third-degree murder based on the theory that Zimmerman had committed a felony - child abuse - against Trayvon.

He was ambushed, he said, because prosecutors had made no mention of the child abuse allegation until Thursday.

"It's outrageous that the state would do that at this stage of this trial. ... Judge, this was a trick."

After lunch, the judge said there was no evidence to support child abuse and ruled for the defense.

Zimmerman says he shot the unarmed, black Miami Gardens teen in self-defense after Trayvon punched him, knocking him to the ground, then climbed on top and began hammering his head against a sidewalk.